I have written earlier about Sam Harris’ book Free Will, particularly a passage on page 8 where he cites the work of Benjamin Libet. To recap, in the 1970’s, Libet used EEG scans to show that activity in the brain’s motor cortex region can be detected approximately 300 milliseconds before a person is consciously aware of having taken a simple decision to move his or her finger or wrist.
This work has been used as an argument against the notion of free will, and Harris doesn’t hesitate to press it into service:
These findings are difficult to reconcile with the sense that we are the conscious authors of our actions. One fact now seems indisputable: Some moments before you are aware of what you will do next — a time in which you subjectively appear to have complete freedom to behave however you please — your brain has already determined what you will do. You then become conscious of this “decision”, and believe you are in the process of making it. (Free Will, pg. 9)
It strikes me as curious that Harris should lean so heavily on an experiment that tests such a simple aspect of conscious human decision making. It is a big leap from trivial finger movements to more decisive or contemplative situations in life, where really significant issues of free will come into play.